IT IS NECESSARY to look very clinically now at Nicaragua. Will it become a totalitarian Soviet-oriented state on the Cuban model, or a Costa Rica-type social democracy, or will the revolution generate a counterrevolution along the lines of post-Al-lende Chile? Nothing inherent in the Nicaraguan scene precludes any one of these outcomes eventually. You can find prophets, hopeful of fearful as the case may be, for all of them. But this is not to say they are all equally likely. The Chilean scenario may be out of the question, at least in the immediate future. But the Cuban one is decidedly not. To reach the Costa Rican outcome, the going is all uphill.

Power is being exercised exclusively by the Sandinista guerrilas, with their various Marxist and Cuban connections. They have the guns. They have the mystique and momentum of victory. They have claimed and applied the right to run everything: government, banks, etc. Nicaragua is today a country in which the interior minister can, as he did the other day, walk into a big hotel where the employees are milling around, pronounce the old manager arrested "for investigation," and select the new manager: total power. The Sandinistas have yet to take any of the three steps that would prove beyond doubt they intend to go the Cuban route: establish a single elitist communist party, move the population into mass organizations controlled by that party, and accept an open affinity with and dependence on a foreign state. They profess to be humanitarians, democrats and nationalists. Fine. But it would foolish to ignore that in revolutionary situations, whatever the real purposes of the leaders - and of course outsiders cannot be sure what these are - events can go a different way.

The Carter administration seems to understand this quite well. It has wisely decided to put a good face on the situation and to keep its doubts to itself, meanwhile extending a hand of welcome, conciliation and aid to the new regime and hoping that this stance will enhance its influence in Managua. You can say it doesn't have much choice, since a negative approach would isolate Washington and might produce or provoke a hostile response. Still, a positive approach puts the United States on the same side as its Latin democratic friends and lets it work with them to ensure that the revolution in Nicaragua actually serves the liberal values its leaders proclaim. In brief, the administration is betting cautiously on the revolution. It is a risky bet, but the right one.